DE 102 06 274 discloses a push-pull chain formed by a plurality of pairs of inner links and outer links, with alternate pairs of the inner links being sequentially coupled to alternate pairs of outer links by parallel driving pins with rollers. The ends of the links are provided with faces which abut in a manner to prevent the chain from bending by rotation of the links about their hinges in one direction but allow the chain to bend freely in the other direction. The faces have a complementary shape to each other so that, when the chain is under pressure, they lie directly against each other to prevent a bending movement. The chain can be used in an actuator with a chain path leading to a chain exit and guiding the chain past a sprocket that engages the rollers to drive the chain. The rollers roll on the guide surfaces of the chain path. The chain path comprises an arc-shaped section concentric with the sprocket to guide the chain along the drive sprocket with the rollers engaging the guide surface. The engagement between the rollers and the sprocket prevents the rollers from rotating, and thus the rollers are not able roll when moving through the arc-shaped section of the chain path. When the chain is under load, the rollers are pressed with a high force towards the guide surface of the chain path in the arc-shaped section, i.e. there where the rollers are engaging the teeth of the sprocket and cannot rotate. The rollers are thus dragged over the arc-shaped section under high load, and the resulting frictional losses reduce the mechanical efficiency of the actuator.
Document U.S. Pat. No. 3,976,166 discloses an elevating device including a push-pull chain provided with central rollers for engaging a sprocket and a curved guide surface that urges the chain around the sprocket. The simultaneous engagement of the sprocket and the guide surface cause the above described problem of dragging the rollers over the guide surface at the location where the rollers are highly loaded, thus causing friction losses.
Document U.S. Pat. No. 5,895,880 discloses a projectile ramming apparatus including a push pull chain provided with lateral rollers guided for engaging two sprockets and a curved channel that urges the chain around the sprockets. The simultaneous engagement of the sprocket and the guide surface result in the above described problem of frictional losses caused by dragging locked rollers.
Document EP 0829659 discloses a hybrid power transmission chain comprising a structure from both roller and silent chain. The inner chain include bushings that ride along the teeth of a sprocket and the outer chain comprises link plate with inverted teeth that engage two other—differently sized and shaped sprockets. This type of chain is not suitable for use in an actuator but it combines the advantages of the wear resistance of a roller chain with the silence of a silent chain. However, due to the low speed at which actuator chains are operated neither of these advantages is relevant in the field of the present invention.